The "Bootable" legacy ISO you've used is in fact not bootable, it relies on CDROM emulation provided by BIOS. VMs don't usually do this sort of emulation. If you set the guest OS to something like ...

The virtual machine may fail to boot from an ISO because the boot order prioritizes the virtual hard disk over the optical drive, resulting in a “No bootable medium ...

Having a virtual machine on-hand can be useful for a variety of purposes, such as testing software or tweaks in a sandboxed environment that is separate from your primary operating system. A virtual ...